Cathode ray tube



Aug. 27, 1940. P. M. G. mm I CATHODE RAY TUBE Filed July 9, 1936 INVENTOR PIERRE MARIE GABRIEL TOULON mane &

ATTORNEY Patented Aug. 27, 1940 CATHODE RAY TUBE Pierre Marie Gabriel Toulon, Puteaux, France Application July 9, 1936, Serial No. 89,707 In France July 9, 1935 2 Claims.

"-'I'his' invention-relates to cathode ray tubes, and-in particular, to-cathode ray tubes adapted fox-"the projection of high intensity images.

The invention covers a new method which per- 5 mits of transforming into a very intensive luminous spot the beam of cathode-ray oscillograp-h,

andespeciallyof projecting on a screen the image resulting from the modulation and from the displacement of'the beam by the deflecting electrodes during the scanning.

The invention can be particularly applied to projection apparatus for television purposes, whose scanning device is a cathode ray tube. It

consists in-using an auxiliary and powerful light source "and in causing the luminous beam emanating from it to strike on the surface that recei-ves atthe same time the cathode ray beam from'the'cathode ray tube, so as to modulate locally the luminous intensity, according to the intensity of the electron beam,- and in causing to appear on the screen an enlarged and luminous image of the televised subject. 7

' The process according to the invention of locally modulating the luminous beam by the impact 26 of the electronic beam may have several variants: Thenegative charges carried by the beam can be utilized directly through the conductivity of the wall by means of conducting rods fixed withinv the insulating mass of the latter, or indirectly 30 by" influence effect.

It is also. possible to utilize the electronic radiation; (Lenard rays) or the electromagnetic radiation (X rays, ultra violet rays, etc.) resulting from the impact of the beam on the anticathode.

In order to modulate the luminous beam one canavail ones self of the displacement or the depositing of material particles on the wall electrified 'by the electronic beam (the particles consisting of sulphur, red lead, etc.) or of the modi- 40 fication of the optical properties of certain substancesiquartz, Cellophane, etc.) or also of the releasing of gaseous bubbles, as well as of electrolytical depositing, cataphoresis, etc. According to the invention, one can usea1ways starting fromthe electronic beameither the deposited electric charges or the current which has been locally engendered, or also, the electromagnetic radiation, in order to ,control the illumination produced by the auxiliary light source. That control can be accomplished by modifying the opacity or the plane of polarization, or the respective position 'of the substances that are suitably distributed on. the surface, etc.

' "Several figuresattached to this specification explain the object of the invention and physical embodiments of it in some particular instances,

The drawing shows in Fig/ 1 a physical embodiment in which the electrified charges p ro-v duced by the cathode beam serve to rotate the 5 plane of polarization of the light; i n

Fig. '2 shows another realization'in which the electric charges cause the displacement of silvered movable leaves; and i Fig. 3 represents anotherphysical embodiment 10 in which the depositing of materials, orelectro-i chemical phenomena, etc., are utilized. I Allthese figures have been given only by way ofexamples.

It is evident that any system which comprises in combination asystem of scanning by means of a cathode beam,'an auxiliarylightfsource, and a local modulation ofthe lig'ht beam by the cathode beam, -in' order to reproduce an image of the source on a*screen-which image is modulated accordingto the intensityof the cathode beam.- comes within the scope of the invention covered by the present patent. V v

Certain substances such as Cellophane; quartz, mica,' etc., have the property of rotating the optical plane of polarization whenan electric po- 25.. tential is applied" betweenjtheir two surfaces. This property is used for bringing'about the pro.- je'ction of a television image on a large screen. (for instance bymeans of the device: described in Fig. '1). The ele'ctronguri I comprises acon- 30 trol grid connected to the radio receiving set, and the deflecting plates 3 and 4 insure thefscanning of the beam in synchronism with the transmitter.

The screen which o'r'dinarily is'metallizled and provided-with a transparent fluorescent substance is here made'up of a very large number of small conducting squares, 1', that are insulated one from the other and arranged on the' optically variable insulating substance 6. A thin metal fi1m 5, pro-. vided on the back of that substance, fixes the 40 potential and has the efiect of creating a high; electric field as soon as a charge is deposited on any one of the small squares I.

The scanning'of the modulated cathode beamhas thus the'e'ffect of introducing on the differ 45- en: successive squares, such as 1, variable negative charges, and these depositedcharges modify theplane of polarization of the substance facing them. A very powerful light source [2 which is polarized by the system l3 illuminates the sub- 50.

stance 6.. By means of the lens ll the light rays are then concentrated on the. objective l 6 and the nicol or other prisms I4. The thickness "of the substance ,6 and the positions of the nicols l3 and 14 are Selected in such a manner that nolight 55-;

will pass unless a charge is deposited on 1. In other words, the objective I6 transmits no light on the projection screen. On the other hand, when the apparatusis operating, charges will be deposited at 1 as a result of the influencing of grid 2 when the set is receiving, and these charges will reproduce the instantaneous image transmitted by the sender. The locally variable rotation of the plane of polarization of layer 6 permits reproducing on the screen a very luminous and enlarged image of the televised object or person. The layer 6 may be made from Polaroid as is well known in the art.

. It is very easy to realize that this image could not, in that shape, be constantly mobile,,for the electrons transmitted by the electron gun tend always to settle in the small squares represented by 1. In order to insure automatically the discharge at the end of a certain time, for instance at the end of each image i. e. every twenty-fifth of a second, it is necessary to bring abruptly to an insulating grid 24,

each one of these little squares positive charges or, what amounts to the same, to remove abruptly from these squares several electrons, in order'to bring them back to the neutral state or, more exactly, to the potential of the electrode 5.

According to the invention, each one of the small elementary squares is itself covered with a photo-emissive substance (for instance, a substance preferably sensitive to ultra-violet-radiation, such as potassium, strontium,-magnesium,

etc.).

At the end of the scanning of each image, for instance, the discharge of the small squares is automatically insured by operating in the following manner: A gaseous discharge tube such as is generally used to produce saw tooth wave energy for the scanning of the images also causes, upon discharging, a mercury tube to light up (one comprising quartz for instance) or actuates by relay means any other appropriate source of light that will furnish a light extremely rich in actinic rays. By means of a system In to concentrate the light, the various elementary cells 1 are enabled to emit electrons, provided their potential is high, that is to say, if they are charged. A grid 8 to which a voltage is applied which is slightly higher than that of wall 5. during the operation captures the electrons and brings thus instantaneously all the little squares I to the common basic potential.

In this manner the apparatus is freed from all the preceding image charges and is now in a position to receive new image charges again, byv

' ing that emanate from the electron gun I9 within the tube, the electrified charges (Lenard rays) that leave it through a window of thin metal, for instance an aluminum foil supported by a grid.

The back of the oscillograph is thenmade up of an enclosure 3 containing a rarefied gas. A metalgrid 2| supports the very thin aluminum foil 22 that separates the cathode-ray oscillograph (which is highly evacuated) from the enclosure containing the rarefied gas 23.

The Lenard rays impinge on the small elementary electroscopes 25 that are supported by and bring about their deviation. If necessary, another conducting grid with a fixed potential, grid 26, may be made to strengthen the field t us created near these electrometers. 1

The inclination of the foils of the various electroscopes is variable and the elementary reflecting surfaces have the effect of transmitting through the objective 29 a variable quantity of light that originates from the light source 28. A lens or other optical system 21 is placed in register with the light beam to improve the efficiency.

At the end of the scanning, the automatic discharge of the difierent electroscopes is accomplished by means of the ionization of the gas in the enclosure 23. To this end, two electrodes l1 and I8 are provided, and a high potential difference is abruptly impressed between them (under the influence of the scanning or synchronizing pulse) this voltage application resulting in a spark discharge.

It is possible also to insure the projection on the screen in conformity with the invention by materializing the cathode image by means of deposits of very fine, dust-like particles. As is shown in Fig. 3, the backof the oscillograph may be made to consist of a material which is sumciently conducting, so that the electrified charges 30 will pass through it. A grid 3| prevents the charges deposited on the walls from disturbing the field in the tube. If at the back of the apparatus in wall 33 a mixture of electrified dustis kept in constant agitation, for instance, flowers of sulphur and minium, one may, through electrostatic influence, obtain the deposit of that. dust mixture on the electrified points (Hirns figures). In order to facilitate the understanding of the phenomenon, I have represented ,in Fig. 3 the reassume their travel within the enclosure, where they are subjected to continuous churning.

I have shown at 37 the container for the powder mixture, 38 is the fan which takes care of the churning of the air and of the propulsion of the dust particles, 39 is the rotor, also within the enclosure, which drives the fan, and 40 is the electric stator connected to' an alternating-current supply line. The powdered particles follow a closed circuit due to the canal 44. The light source 4! illuminates the back of the cathoderay oscillograph, which is preferably silvered and concave in order to increase the luminous efiiciency. The reflected rays are concentrated on the objective 42 and thence goto the screen 43. The deposit of opaque material particles at points such as 36, corresponding to the scanning by the beam and to reception of television, has the effect of reproducing on the screen the continuous image of the televised subject, and to do this faithfully, both as regards size and intensity.

In the figures which I have given here by way of example I have assumed that the surfaceontion), but it is evident that one can also operate by using the transparency principle, that is to say by placing the lamp and the objective on both sides of that surface respectively.

It goes without saying that the invention is not limited to television purposes. It can be applied to cathode oscillographs and the like apparatus, and in general to any system of scanning involving cathode ray beams.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The method of projecting images, comprising the steps of developing a source of radiant energy, developing a beam of electrons, developing a source of polarized light, projecting the polarized light upon a light polarizing medium having a predetermined plane of polarization, varying the plane of polarization of the developed medium by the developed beam of electrons, and subsequently photoelectrically restoring the plane of polarization of the medium to its original p ane.

2. In combination, an envelope having a transparent end wall, an electron gun to develop a beam of electrons within said envelope, a light polarizing layer mounted on the end wall, a plurality of minute photoelectric activated bodies mounted on said layer, means to direct the beam of electrons upon the plurality of photoelectric activated bodies, a source of polarized light directed upon the light polarizing layer, a polarized light analyzer and optical system in register with the end wall, a source of light directed upon the photoelectric activated bodies, said source being activated to emit light only during predetermined time intervals.

PIERRE MARIE GABRIEL TOU'LON. 

